1. Field of the Invention
This invention relates to a medical optical apparatus which uses a plurality of light each having a different wavelength.
2. Description of the Prior Art
As examples of surgical operation using a medical optical apparatus such as a medical microscope, there are cerebral surgical operation and ophthalmological operation. The ophthalmological operation includes an operation to be made on a bottom part of a vitreous body (i.e., vitreous body operation). The bottom part of the vitreous body is of a multi-layer structure having layers of a retina, a chorioidea and a sclera arranged in this order from the vitreous body.
For operation of this vitreous body, three holes, called ports, are formed in a side portion of an eye to be tested (patient's eye). One of these three ports is used for maintaining an intraocular pressure, another one of the remaining two ports is used for insertion of an optical fiber for illumination, and the last one is used for insertion of an operating instrument. For operation, the retina at the bottom part of the vitreous body is illuminated by the optical fiber and an objective part (diseased part) of the retina is operated using the operating instrument while observing the illuminated diseased part through a medical microscope.
A visible light is usually used for illumination during such operation. However, since the visible light is absorbed by the upper skin (or epithelium) layer of the retina, the patient's diseased part under the retina cannot be observed during the operation. Since only the visible light is used for observation of the bottom part of the eye to be tested, observation is limited. For observation of an inner side of the upper skin (or epithelium) layer of the retina, it can be contemplated that a fluorescent agent is injected into the patient's vein to send the fluorescent agent to a blood vessel of an eye fundus, and on the other hand, fluorescent excitation light is irradiated to the eye fundus so that the fluorescent excitation light is absorbed by the fluorescent agent which is still remained in or already leaked out of the blood vessel of the eye fundus, in order to excite the fluorescent agent, and then, the fluorescent light from the fluorescent agent is observed to check the diseased part in the upper skin (or epithelium) layer of the retina. This fluorescent observation is performed under a visible fluorescent light or an infrared fluorescent light. In this case, it is preferable that the visible fluorescent excitation light, the infrared fluorescent excitation light, the visible illumination light, and the infrared illumination light can be switched to one another so that the light can be selectively irradiated to the eye fundus or several kinds of light can be irradiated to the eye fundus simultaneously. In the medical optical apparatus such as a medical stereoscopic microscope, an illumination light from an illumination light source is projected to an observation part through an illumination optical system, and an image to be observed formed by the light reflected from this observation part is guided to an ocular lens through two main optical paths of the observation optical system, so that the operator can observe the observation part (for example, operating part, etc.) by his two eyes.
It is also necessary for an assistant operator to be able to observe the observation part in the same manner as the operator because the operation is cooperatively performed by the operator and the assistant operator. To this end, the medical stereoscopic microscope is provided with a sub-observation optical system branched from a midway of one of the main optical paths so that the assistant operator can also observe the observation part during the operation.
In a recent method of a medical treatment, it becomes more frequent to use an infrared light or light of a wavelength area low sensitive or hardly sensitive to a human eye such as a wavelength of about 400 nm or 700 nm (the light in this wavelength area is generally referred to as "invisible light"). For example, in a department of cerebral surgery, a malignant tumor is extracted by utilizing the nature of the fluorescent substance liable to selectively remain in a cancerous cell, or in an ophthalmological department, a deep layer of the retina is optically solidified by utilizing an infrared laser beam of light in order to arrest the progress of the patient's disease.
Heretofore, the optical solidification operation is performed while observing the diseased part under the visible light. However, since the human eye is not sensitive to an invisible light, it is usually difficult to observe the diseased part by naked eyes under this invisible light.
In order to observing the diseased part under this invisible light, it can be contemplated that a part of the reflected light from the observation part is extracted from the other optical path of the main observation optical system and guided to, for example, a TV camera sensitive to an ultraviolet light and a TV camera sensitive to an infrared light, so that the observation part is taken by the TV camera and displayed on a monitor TV.